1. Field of the Invention
The present invention relates to an adjustment method using an image restoration processing, an adjustment apparatus, a method of manufacturing an optical system, an image pickup apparatus, and a method of manufacturing the image pickup apparatus.
2. Description of the Related Art
A method of correcting a blurred image that is generated by aberrations of an optical system by digital processing using information of an optical transfer function (OTF) is known. This method is called an image restoration or an image recovery, and hereinafter, the processing of correcting a deterioration of an image using the information of the optical transfer function of the optical system is referred to as an image restoration processing or a restoration processing. In an actual manufacturing setting, production variability is generated for a performance of the optical system because of a production error of a lens, a production error of a barrel that holds the lens, or the like. When there is a difference between aberration characteristics that are generated in an actual shooting and aberration characteristics that are assumed in the restoration processing, a negative effect such as a ringing may be generated as an artifact in a restored image. Therefore, the production variability may give the negative effect to the restored image. Previously, as a method of reducing the production variability, adjustment of decentering a part of the optical system or an image pickup element for the optical system having the variability has been performed.
On the other hand, Japanese Patent Laid-Open No. 2009-9593 discloses a method of including the image restoration processing as an evaluation reference at the time of adjustment to perform the adjustment considering a total performance including the image restoration processing. Japanese Patent Laid-Open No. 2008-85697 discloses an adjustment method considering the production variability. In Japanese Patent Laid-Open No. 2008-85697, a plurality of aberration characteristics are prepared at a side of an image pickup apparatus and the optimum aberration characteristic is selected in accordance with the production variability to reduce the production variability.
However, in the method disclosed in Japanese Patent Laid-Open No. 2009-9593, the performance variability that finally remains when the production variability is generated in the image pickup apparatus is emphasized by image restoration processing. In order to avoid this, a parameter in generating a restoration filter needs to be changed to adjust the balance with an amount of the negative effect while decreasing the level of the restoration. In the method disclosed in Japanese Patent Laid-Open No. 2008-85697, the restoration filter is stored in the image pickup apparatus and therefore a memory capability of the filter is enlarged. The restoration filter that is used in the image pickup apparatus is determined by at least one parameter of an image height, a focal length, an object distance, Fno (F-number), and an image stabilizing state of the image pickup apparatus. Accordingly, the restoration filter that includes the production variability needs an enormous memory capability.